Diabetic nephropathy is the most frequent cause of end-stage renal disease in the industrialized world. Reduction of dietary protein intake has been implemented for decades to improve the symptoms and slow down the progression of chronic renal disease, including diabetic nephropathy. Unfortunately, this approach is often hindered by poor patient compliance. Evidence from other investigators and our preliminary studies suggest that manipulation of the quality of dietary protein may be as effective as reduction of the total amount of ingested protein in slowing down the progression or preventing the onset of diabetic renal disease. We propose that soy protein, a plant protein relatively high in essential amino acids and with high nutritional value, may be particularly beneficial to Type 1 diabetic patients with incipient renal disease. The hypothesis is submitted that substitution of soy protein for animal protein in the diet of Type 1 diabetic patients with incipient nephropathy will normalize elevated glomerular filtration rate and correct microalbuminuria. These changes are interpreted as beneficial in the prevention and treatment of early stage diabetic nephropathy. This hypothesis will be tested with a randomized, parallel-design, dietary intervention trial in Type 1 diabetic patients with elevated GFR and microalbuminuria. The patients will be randomized to a soy protein-based diet, or a carefully matched animal protein-based diet, for 16 weeks. Specific aims of the study are to determine whether soy protein intake, compared to animal protein intake, is associated with: Number 1.: Reduction in microalbuminuria. Number 2.: Amelioration of glomerular hyperfiltration. Number 3.: Reduction in both total and oxidized LDL-cholesterol. Although it has long been suspected that plant protein diets may be superior to animal protein diets in the management of chronic renal insufficiency, this is the first time that the effect of these two diets will be compared in a well controlled study in patients with Type 1 diabetes and incipient nephropathy. If the above hypothesis proves correct, it will have far reaching implications in the management not only of Type 1 diabetic patients but, possibly, of all individuals at risk of developing chronic renal disease. Additionally, this study will provide solid rationale for future animal and in vitro studies aimed at revealing the mechanism(s) that underlie the proposed beneficial effects of soyfoods in kidney disease.